Process for the preparation of low torque crimped textile yarn



United States Patent O i I 3,399,524 V PROCESS FOR THE PREPARATION OF LOW TORQUE CRIMPED TEXTILE YARN Takao Koizumi, Komatsu-shhlapan,assignor to'Teijin Limited, Osaka, Japan, a corporation of Japan I No Drawing. Filed July.-23, 1964, Ser. No. 384,799

Claims priority, application Japan, Aug. 9, 19.63,

38/412,287; June 23, 1964, 39/315,442

.3 Claims. (Cl. 57-157) ABSTRACT OF THE DISCLOSURE A process for forming low torque yarn by high-twisting a yarn of thermoplastic synthetic filaments until double twisting occurs, setting the twist and then untwisting to leave a residual twist of between 50 800 turns per meter.

This invention relates to a process for the preparation of low torque crimped textile yarn. More particularly, the invention relates to a process for the preparation of low torque crimped textile yarn having a pleasant dry (not sticky) and composed of thermoplastic synthetic filaments such as polyamide, polyester, polyethylene, propylene, polyvinyl chloride, polyacrylonitrile, etc.

Crimped textile yarns prepared from those thermoplastic filaments by the steps of twisting, heat setting and untwisting are known. These shall be hereafter referred to as twist crimped bulked yarns. However, the yarns prepared by the known process have such a deficiency that, because of their high torque, the knitted goods prepared from them tend to have the wales distorted. One method of reducing the torque is to ply together the yarn twisted in S-direction and that twisted in Z-direction to offset their torque in the opposite directions, but such is costly and the products have inevitably large deniers.

Another method of reducing the torque without plying but using the single yarn comprises first high-twisting the yarn, setting the high twist and untwisting the same, again high-twisting the same in the direction opposite to that of the first high-twisting, heat-setting it and then untwisting the same. The purpose of the above is to offset the torque imparted to the yarn by the first series of high-twisting, heat-setting and untwisting, with the torque resulted from the second series of high-twisting, heat-setting and untwisting in the opposite direction. The process is advantageous in that, because it does not use a plying technique, a fine denier product can be obtained. However, since by that process repetition of twisting, heat-setting and untwisting twice is required, the operation is complicated. Besides, equipment and operational costs are high. The practice of the process also requires many workers and the control is difiicult.

The object of this invention is to provide crimped textile yarn devoid of the aforementioned deficiency, that is, to provide low torque, crimped textile yarn prepared from single yarn made of thermoplastic synthetic filaments at low cost.

Other objects of this invention will be obvious from the contents of the specification hereinafter disclosed.

It is found that the objects of this invention can be achieved by treating a yarn of thermoplastic synthetic filaments, which has been high-twisted in one direction to the degree that a least some double twisting occurs and which then has been set, in such a manner that the twist in the same direction as of the first high-twisting in the order of 50800 t./rn. (turns per meter) should be finally retained in the treated yarn.

The treatment may be varied depending on the type of the twister employed. For example, when the conventional twister (so-called up-twister) is employed, the yarn 3,399,524 Patented Sept. 3, 1968 is first twisted to the degree that at least some double twisting starts to occur, followed by setting, and then it is untwisted leaving the twist in the order of 50-800'tl/m. in the yarn, to wit, untwisted by the number of the first twisting minus -50-800 t./m. Thus the crimped textile yarn intended in this invention can be obtained. Again when a false twister is used, the yarn is first twisted by the false twister to the degree that some double twisting starts to occur,-followed by setting and complete untwisting tie. to O t./m.), and then again twisted in the same direction as the first twisting by 50800 t./m. with a suitable twister. Or, a yarn imparted with twisting of 50-800 t./m. with a suitable twister in advance may be subjected to ahigh-twisting with a false twister in the direction of the previously given twisting to the degree that some double twisting starts to occur, followed by setting and untwisting.

Generally speaking, double twisting starts to occur when the number of twist (t./m.) reaches about 29,200/ /denier. The critical number of twist at which the double twisting occurs however varies somewhat on such factors as the type and denier of the particular yarn, structure of the twister (for example, frictional coeificient of the spinner in a false twister), tension on the yarn, etc. For example, in case of 210 denier-nylon yarn, with the increase in tension by each 0.1 g./denier the critical number of twist increases by about 60-70 t./m. Once the double twisting starts, before the yarn becomes double-twisted over its entire length, about 1000 t./m. of additional twisting is required for a 210 denier-nylon yarn, and about 1500 t./m. twisting for a denier-nylon yarn. In order to achieve the objects of this invention, such 100% double twisting is not necessarily required. For a practical purpose, above 10%, preferably about 2080%, double twisting is sufficient. However when an up-twister is employed, that of about 25% is preferred because in the said twister the tension on the yarn varies with the time passage.

The degree of double twisting which has taken place can be measured by such means as taking a photograph at the exposure of no longer than 7000 second, or by suddenly stopping the machine and observing the state of twisting.

The setting of the twist can be preferably effected with heat as such will enable a continuous working; however, it can also be done with suitable chemicals. For example, for polyamide-type yarn, 2% aqueous solution of phenol or methacresol can be used for this purpose. Heat-setting can be effected either by dry heat or wet heat, and the temperature and time can be selected from the ranges usually adopted in known heat-setting operation. For example, in case of dry heat-setting 6-nylon yarn in a false twister, -190 C. heating for 0.2-3 seconds is suitable, and in case of steam setting the same in the form of hank, 100-130 C. heating for 20-30 minutes is suitable.

The crimped textile yarns thus obtained in accordance with the process of this invention have a very much lower torque compared with conventional twist crimped bulked yarn, and have a pleasant dry hand. When the yarns are further dry heat-treated or wet heat-treated, still better results can be obtained as to the reduction of torque and/ or increase in bulk.

For example, a stocking knitted from 21.0 denier-nylon crimped yarn which is false-twisted to a degree not having any double twisting has its stitches biased by about 25-30". Whereas, from the crimped textile yarn treated in accordance with the process of this invention, a stocking can be prepared in which the angle of torsion is within the range as will not offer any practical difiiculty or drawback. Further, when the crimped textile yarn of this invention is treated as continuously running single strand with dry or wet heat of ISO- C. for 0.2-1 second, or when treated in hank form with dry or wet heat of 70130 C. for 5-20 minutes, the yarn can be still improved and will give stockings in which the angle of torsion in the stitches is further reduced by 20-50%.

Generally, yarns subjected to the steps of twisting, setting and untwisting have latent crimp, besides the crimp visible on the surface. Therefore, before performing the said heat'treatment to further reduce the torque, the yarn may be allowed to stand for along period (for example, 24 hours or longer), or heat-treated at milder conditions than the foregoing (in case of treating a continuously running yarn, the heating may be by dry heat or wet heat at 100-160 C. for 0.2-1 second, and when the yarn is treated in hank form, 4090 C. for 5-30 minutes), or treated with a swelling agent, to develop the latent crimp into visible crimp in advance, to be imparted with even greater bulk. In case of polyamide yarn, for example, when it is wet heat-treated in hank form at about 5065 C. for 2030 minutes so that its latent crimp will develop into visible crimp, and thereafter further heat-treated at 100-130 C. for -20 minutes, highly bulky, low torque crimped textile yarn having a pleasant dry hand can be obtained.

The pleasant dry hand obtainable by the subject process is probably due to the fact that among the crimps resulting from the single twisting, wave-like large crimps resulting from the double twisting are present in places.

The present invention is further illustrated by the following nonlimitative examples.

Example 1 Nylon yarn of 210 deniers/24 filaments was hightwisted by 2410 t./m. by means of a false twister under a tension sufiicient to cause the occurrence of double twisting, dry heat-set at 185 C., and thereafter untwisted. Then the yarn was further twisted in the direction of the aforesaid false twisting by 450 t./m. and wound onto a hank, which then was wet heat-set at 40 C. for 30 minutes so that its latent crimps would develop. Thus excellent single crimped textile yarn having a low torque and a unique hand as shown in Table 1 below was obtained.

Nylon yarn of 210 deniers/ filaments was twisted by 2400 t./m. by means of a false twister under a tension sufiicient to cause the occurrence of double twisting, dry heat-treated at 185 C., and then untwisted. The yarn was further twisted by 750 t./rn. in the direction of the false twisting and wound onto a hank. The hank was then wet heat-set at 110 C. for minutes. Thus an excellent single crimped textile yarn having a low torque and a unique, pleasant dry hand was obtained. The product yarn had a crimp elongation of 50.5%, and the knitted goods prepared therefrom had its wale distorted only by 5.

Example 3 Polyethylene terephthalate yarn of 225 denier:;/ 108 filaments was twisted by 3200 t./m. by means of an uptwister under a tension sufficient to cause the occurrence of double twisting, and steam-treated at 160 C. for minutes, followed by untwisting as would leave 200 t./m. of the initially imparted twists in the yarn. The resultant yarn was wound up onto a hank, and subjected to a heattreatment for an hour, during which the temperature was gradually raised from room temperature to 120 C. Thus an excellent low torque crimped textile yarn having a crimp elongation of 65.0% was obtaine The knitt 4 goods prepared therefrom had its wale distorted only by 6.

Example 4 A yarn of 210 deniers/102 filaments (prepared by paralleling three deniers/34 filaments) was first twistedin Z-direction by 5t) t./m. by means of an uptwister and then false-twisted by 2400 t./m. also in Z direction by means of a false twister under a tension sufficient to cause the occurrence of double twisting. The yarn was then dry heat-set at 180 C., followed by untwisting and then wound onto a hank. Thus, a crimped, low torque textile yarn having a crimp elongation of 89.5% was obtained. The knitted product prepared therefrom had a wale distorted only by 6.

Example 5 Acrylonitrile yarn of 100 deniers/30 filaments was twisted by 3400 t./m. by means of an up-twister under a tension sufficient to cause the occurrence of double twisting, followed by steam-setting at 120 C. for 30 minutes. Then the yarn was untwisted leaving 150200 t./m. of the initial twists in the yarn and wound up onto a bank. By subjecting the bank to a setting at 60 C. for 30 minutes, crimped textile yarn having a low torque and a crimp elongation of was obtained. The knitted product prepared therefrom had its wale distorted only by 5.

Example 6 Polyvinyl chloride yarn of 150 deniers/50 filaments was given 2500 t./m. of false twisting by means of a false twister under a tension sufiicient to cause the occurrence of double twisting, which was set by passing the yarn through hot water of C., and then untwisted. Then the same yarn was given a twisting of 180 t./m. in the direction of the false twisting, and wound up onto a hank. By dry heat-treating it at 60 C. for 20 minutes, highly crimped, low torque textile yarn having a crimp elongation of 82.0% was obtained. The knitted product prepared therefrom had its wale distorted only by 5.

Example 7 Nylon yarn of 210 deniers/24 filaments was given a false twisting of 2410 t./m. by means of a false twister under a tension sufficient to cause the occurrence of double twisting, and dry heat-set at 180 C., followed by untwisting. Then the yarn was given a twisting of t./m. in the direction of the false twisting, and wound up onto a hanks to be left as it was for 24 hours. Thus a low torque, bulky crimped textile yarn was obtained. When the same was further treated with steam of C. for 20 minutes, more bulky, crimped textile yarn having a still reduced torque was obtained.

The properties of the above yarn are compared with those of the control product, which was treated exactly in the same manner as in the above except that the initial number of false twist was 1660 t./m. (with such a degree of twisting, double twisting does not occur), as in Table 2 below.

TABLE 2 Torsion in stitches (d a Before steam treatment 7 Example 7 "{Atter steam treatment 4 Control Before steam treatment 36 having a twist in the order of 50-800 turns per meter by means of a false twister wherein at least some double twisting occurs, in the direction of the initially possessed twist, setting the high-twist and then untwisting the same.

3. A process for the preparation of low torque, crimped textile yarn which comprises high-twisting a yarn composed of thermoplastic synthetic filaments wherein at least some double twisting occurs, setting the twisted yarn, untwisting the same, and then wisting it by 50-800 turns per meter in the same direction as the high-twisting.

References Cited UNITED STATES PATENTS 8/1958 Billion 57-157 1/1962 Heberlein et al. 57157 X 3/1964 Baebler 57-157 X 1/1965 Servage 57-157 X 10/1914 Moller 2872 10/ 1951 Underwood et a1. 2872 10/1948 Clarkson 57156 FOREIGN PATENTS 2/ 1964 Australia.

6/1959 Great Britain.

8/ 1959 Great Britain.

7/ 1965 Great Britain.

STANLEY N. GILREATH, Primary Examiner.

D. WATKINS, Assistant Examiner. 

